The present invention relates to a method of and an apparatus for detecting a coordinate position.
The present application claims priority from Japanese Application No. 2004-100131, the disclosure of which is incorporated herein by reference.
As a prior art for the present invention, Japanese Unexamined Patent Application Publication No. 2001-306241 discloses a coordinate position detecting method adopted in an optical touch panel or the like. This method detects a coordinate position on a display surface by using detection beams to scan in the horizontal direction and the vertical direction (X axis, Y axis) which are orthogonal to each other on a two-dimensional display surface, thereby detecting the position of a shading object touched on the display surface, in accordance with the scanning positions of the detection beams shaded by the shading object.
FIG. 1 is an explanatory view showing the above constitution. As shown, a plurality of light emitting elements 2X are arranged in X axis direction along one side of the display surface 1, while a plurality of light receiving elements 3X are arranged opposite the light emitting elements 2X. Further, a plurality of light emitting elements 2Y are arranged in Y axis direction along another side of the display surface 1, while a plurality of light receiving elements 3Y are arranged opposite the light emitting elements 2Y. In this manner, each line of the light emitting elements 2X, 2Y are lighted so as to emit light beams LX and LY successively from one end to the other. The emitted light beams LX and LY are then detected by the light receiving elements 3X, 3Y. Accordingly, the coordinate position of the shading object which is a point P on the display surface 1 can be detected by light receiving elements 3xp, 3yp shaded by this point P.
On the other hand, Japanese Unexamined Patent Application Publication No. 2001-306241 further discloses that when detecting the coordinate position of a continuously moving shading object, a changeover is performed between a full scanning (a first scanning) mode and a short scanning (a second scanning) mode.
In the above-described prior art, the first scanning mode is a mode for scanning an entire area corresponding to the width of the display surface, enabling the light emitting elements arranged corresponding to the width of the display surface to successively emit light beams from one end to the other so as to effect a scanning (refer to FIG. 1). Such a scanning is adopted in detecting an initial position of a shading object.
On the other hand, the second scanning mode is a mode for scanning in a narrower range than the entire area containing a coordinate position detected in the first scanning mode, lighting the light emitting elements in succession and thus effecting a scanning within such a narrow range. Actually, this mode is adopted for continuously detecting a shading object. As long as the detection is being continued, the position of a shading object to be next detected will be in the vicinity of the position of the shading object which has just been detected. For this reason, a scanning area is limited to a local area (refer to FIG. 1) corresponding to a few light emitting elements, so as to shorten a scanning period by taking into account a moving direction and a moving speed which can be found from the history of detection position when the detection is continued. In this way, if a line (for example) is to be drawn, it is possible to perform a continuous position detection at an exact response speed, thereby ensuring a position detection not involving any detection miss.
However, if for example a character is drawn on the display surface by virtue of a shading object, especially when a plurality of characters are drawn thereon, the detection process will be interrupted between one character and another (i.e. the shading object will move away from the display surface). Moreover, even only single one character is drawn, there is still a possibility that the detection process will be interrupted between one stroke and the another. At this time, although the shading object is moved from one stroke to another or from one character to another within an extremely short time, the aforementioned coordinate position detecting method which performs a changeover between the first scanning mode and the second scanning mode will change its current scanning mode over to the first scanning mode at the time the detection of the shading object is interrupted. As a result, it takes a relatively long time in performing a next position detection, hence increasing a possibility that the position detection will be interrupted at the start of drawing a next character.
Actually, the above problem occurs not only in drawing characters, but also in moving the shading object at a higher speed than the follow-up speed of the second scanning mode (when the movement of the shading object is being continuously detected). Namely, if a straight line is drawn at a high speed, the follow-up speed of the second scanning mode will not be quick enough and the shading object will move away from a second scanning area. As a result, at a time of a next detection only a detection based on the first scanning mode can be performed, and a detection miss is likely to occur in character drawing performed right after the shading object has moved away from an area of the second scanning mode.